Over the past decade treatment of the growth hormone deficient (GHD) pediatric with replacement GH (recominant somatropin) has become a routine practice. However, the discontinuation of treatment upon attainment of targeted height theoretically yields a patient population that is GH deficient during adulthood. It is therefore expected that adulthood for such patients will be characterized by the metabolic consequences of inadequate endogenous GH action. The primary objective of the proposed study is to demonstrate that following discontinuation of GH therapy there will be a negative alteration of metabolic variables with associated changes in body composition whereas continuation of GH therapy beyond cessation of linear growth will positively effect both metabolism and body composition toward a more normal and healthy adult state. The rationale for our hypothesis is based upon clinical data from a large number of European studies involving well-defined adult GHD patients. Results from these indicate that adult GHD is a specific syndrome with reproducible signs and symptoms that can be corrected with GH replacement. In the proposed study, adolescents receiving GH therapy and documented to be GHD at the discontinuation of their growth phase will be randomly allocated between two groups to continue therapy with either Genotropin or placebo and followed for two years. Adolescents who do not meet the criteria for GHD at the discontinuation of their growth phase will stop GH and be given the opportunity to participate in the study as an untreated control group and be evaluated at the end of one and two years of no hormone replacement. Replacement drug efficacy will be assessed by within and between group changes of metabolic and functional variables from baseline to year two.